The concept of dimensioning stems from the thought that shipping charges should not be determined solely based on the weight of an object, but also based on its dimensions, to account for the amount of space taken up in a warehouse or on a transport carrier such as an airplane, a ship, a railway car or a truck. In practice this means that, in addition to being weighed on a scale, cargo objects are also measured, either manually or with an automated dimensioning apparatus, to determine their so-called dimensional weight, also known as volumetric weight or cube weight, which is based on the length l, width w and height h of a shipping object and a density factor D set by the shipping company. When accepting an object for shipment, its dimensional weight Wdim=l×w×h×D and its actual weight (determined by weighing the object on a scale) are compared to each other and the price of shipping is based on the larger of the two weight values. The rationale for this is that light-weight goods occupying a large volume should be priced according to the amount of space taken up rather than based on weight in order to promote compact packaging of goods and efficient use of available cargo space on carrier vehicles and in storage facilities.
On their way from the sender to the recipient, the objects often pass through several distribution hubs where they are transferred from one carrier vehicle to another, which can involve different modes of transportation including airplanes, ships, railways, trucks, conveyors and forklift vehicles. At each transfer, the dimensions of the objects, and often their weights, are determined, in order to make optimum use of the available cargo space while avoiding the risk of overloading.
Objects can be lost or damaged in transport. The ability to track objects along their transportation path is therefore important. If an object disappears, for example because of theft or because it was loaded on the wrong vehicle by mistake, its last known location must be established and proven. Or, if an object was damaged in transit, the last location passed by the object in undamaged condition as well as the first location where the object arrived in a damaged state must likewise be found and documented. This is an important aspect in settling liability disputes and insurance claims.
The dimensional weight of an object can be determined by manually taking measurements and entering the data into a computer system, which is the procedure commonly used at the retail locations of postal service organizations and parcel-shipping companies. However, in large-scale facilities where many shipments are processed at a fast pace and out of sight of the customer, such manual methods are error-prone and can result in either overcharging or undercharging a customer. In response to this problem, various methods and solutions have been developed to determine the dimensional weight of objects in distribution facilities and warehouses, including laser-ranging and laser-scanning systems.
Devices for the automated determination of dimensional weight of an object, also referred to as dimensioning systems, belong to the known state of the art, for which WO9427166 (U.S. Pat. No. 6,177,999) may be cited as an example. A collimated light beam is moved across a belt conveyor by means of a deflector unit, in this case a rotating mirror polygon combined with a parabolic mirror, so that objects moving on the conveyor belt are scanned line-by-line. The plane of the scanning beam is inclined by a small angle of incidence θ relative to the surface normal of the conveyor belt, and the height of a point of incidence on the object from the level of the conveyor belt is determined by photographic triangulation of the reflected light returning from the object.
A system for mapping the three-dimensional surface geometry of objects which is described in U.S. Pat. No. 7,215,430 B1, uses LIDAR (the term is thought to be a composite of “light” and “radar”), a remote sensing technology that measures distance by illuminating a target with a laser and analyzing the reflected light. The object is surveyed from a single viewing point and recorded in the form of a so-called point cloud representing the sensed positions of the sensed points of the target surface in a form that may be further processed with CAD Software Tools.
The system proposed in U.S. Pat. No. 7,215,430 B1, which generates an image of a stationary target object from a single perspective, is however not suitable for the purpose of tracking objects in transport, as the objects usually present themselves randomly at different viewing angles.
State-of-the-art dimensioning systems of the kind manufactured by the assignee of the present invention generally contain a plurality of scanners, each of which has a laser light source, a deflector device and a light receiver arranged inside one compact scanner unit. A modulated laser beam emitted by the light source is swept by the deflector unit in a fan-like manner over the object, so that the point of incidence of the laser beam moves over the surface of the object along a scan line. For in-motion scanning of objects traveling on a conveyor belt, the sweep of the laser beam moves in a plane transverse to the travel direction of the object, so that successive sweeps of the laser beam intercept the surface of the moving object along parallel scan lines.
Objects can also be dimensioned while they are in a stationary position. The scanners used in this case have deflector units which not only move the laser beam in fan-like sweeps, but simultaneously swivel the plane of the sweeping movement, so that the scan covers a surface area of the stationary object. As an alternative, the state of the art also includes dimensioning systems where the scanned object is at rest, while the one or more scanners are moved in a controlled manner relative to the object.
Reflected light returning from the object is optically focused onto the light sensor. At discrete points in time, based on the time delay or phase shift between the emitted light and the received light, the distance traveled by the light is calculated. The travel distance together with the known spatial direction of the laser beam at that same point in time allows the position of the point of incidence on the object surface to be determined in spatial coordinates.
The totality of surface points determined in this manner by the one or more scanners of a dimensioning system can be assembled in a so-called point cloud which represents a three-dimensional virtual model of the object surface. From this three-dimensional model, the length l, width w and height h, and thus the dimensional weight D, can be determined for any object regardless of its shape and its orientation relative to the scanners and/or regardless how the object is positioned in relation to the travel direction of a conveyor belt on which the object could be travelling.
In addition to determining the phase shift or time delay of the light returning from the target object and calculating the surface contours of the objects under investigation, laser range finders, including those used in dimensional weight systems, also measure the intensity of the returning light. Since a low intensity level of the returning light goes together with a low signal-to-noise ratio, the intensity values can be used to verify the integrity of the measurement.
It has occurred to the inventors that the intensity data that have heretofore been gathered only for the purpose of validating the time delay or phase shift data from which dimensional weights are calculated could also be used to tint the surface of the three-dimensional virtual model in monochromatic tones corresponding to the intensity levels. Based on the three-dimensional surface-tinted model, grayscale images of the object from any viewing angle exposed to the scanner rays could then be synthesized on demand.
The present invention therefore has the objective to propose a method, whereby based on the data gathered by a dimensioning system, including the intensity values, a three-dimensional model of the scanned object is assembled and stored for the purpose of documenting the presence as well as the appearance of the object at the time and place of the scan, and to further propose a system with the capability to perform the method.